Driver-side airbag module assembly

Abstract: A driver-side air-bag module (14) is mounted to a steering wheel assembly mounting bracket (102) having three mounting apertures (112). The module (14) comprises a cover (20), an inflator (80) and a base plate (40), which are assembled without using fasteners. The base plate (40) has a plurality of arcuately-spaced mounting apertures (52a,52b,52c,52d, 52e,52f) and mounts three studs (60a,60b,60c) . The cover (20) includes a plurality of mating flexible tangs (28a,28b,28c,28d,28e,28f) having locking shoulders (32a,32b,32c,32d,32e,32f) . The inflator (80) has a peripheral mounting flange (86) which includes three arcuately-spaced locking blades (92a, 92b,92c) and a plurality of locking tabs (88a,88b,88c, 88d,88e,88f) projecting from its surface. The base plate (40) has three mating openings (48a,48b,48c), each having an adjacent locking abutment (50). The studs (60a,60b,60c) are first staked to the base plate (40). The cover (20) is assembled by inserting the tangs (28a-28f) through the base plate mounting apertures (52a-52f) so that the shoulders (32a-32f) snap over to engage the base plate (40). The inflator locking blades (92a-92c) are pushed through the base plate mating openings (48a-48c) and twisted to pass them over the locking abutments (50). This traps the base plate (40) between the blades (92a-92c) and the mounting flange (86) and abuts the locking tabs (88a-88f) with the cover tangs (28a-28f), preventing their removal. Three inflator mounting flange slots (90a,90b,90c) receive the studs (60a-60c) during assembly. The air-bag module (14) is installed by projecting the studs (60a-60c) through the steering wheel assembly mounting bracket apertures (112), where spring fingers (114) snap into stud grooves (68a,68b, 68c) to prevent removal. The locking tangs (28a-28f), tabs (88a,88b) and base plate apertures (52a-52f) are unequally spaced, and the studs (60a-60c) and mounting flange slots (90a-90c) are unequally spaced to assure a predetermined orientation of the module (14) when installed.

Description: This invention relates generally to a vehicle air-bag module and, more particularly, to the construction and mounting of a driver-side air-bag module as specified in the preamble of claim 1. Most passenger vehicles are now fitted with driver-side air-bags. These air-bags are usually contained in a module which is secured to the vehicle steering wheel assembly by rivets or threaded fasteners. These modules contain an inflator, a container mounting the inflator and the air-bag, and a functional and decorative cover enclosing the air-bag. The cover has tear lines which the inflating air-bag ruptures to form doors which open to enable the air-bag to deploy. The cover is usually attached to the container by rivets, as is the air-bag and inflator. The air-bag module normally utilises numerous fasteners and stampings to assemble the component parts together into a module and to mount the module to the steering wheel assembly. Consequently, the structure is complex and assembly thereof is time-consuming. A driver-side air-bag module of reduced complexity which is assembled solely through the use of interengaging surfaces on the component parts and which requires no additional fasteners, is known from DE-A-4205726. It would be further desirable to provide a driver-side air-bag module in which the component parts are assembled by using a minimum number of manual manipulations. An air-bag module according to the present invention is characterised by the features specified in the characterising portion of claim 1. It is therefore an object of this invention to provide a driver-side air-bag module of reduced complexity which is assembled solely through the use of inter-engaging surfaces on the component parts and which requires no additional fasteners. Another object of this invention is to provide a driver-side air-bag module in which the component parts are assembled by using a minimum number of manual manipulations. In one preferred embodiment of the invention, this invention features an air-bag module which mounts to a steering wheel assembly that has a mounting bracket. The module comprises a base plate, an air-bag having a mounting collar having a plurality of arcuately-spaced mounting apertures, a cover, and a flanged inflator. The cover has a plurality of arcuately-spaced flexible mounting tangs receivable in the base plate mounting apertures, each tang having a locking shoulder engageable with the base plate when assembled thereto. The inflator mounting flange includes a plurality of arcuately-spaced locking tabs, each one engageable with a locking tang when the inflator is assembled to the base plate to lock the cover and the base plate together by blocking removal of the tangs through the base plate mounting apertures. Co-operating locking means on the inflator mounting flange and the base plate secure the inflator to the base plate. Air-bag securing means secure the air-bag mounting collar to the assembled module. Fastening means carried by the module attach the module to the steering wheel mounting bracket. This preferred embodiment of the invention features an air-bag module that is mountable to a steering wheel assembly which has a mounting bracket having three spaced mounting apertures. The module comprises a base plate, an air-bag, a flanged inflator and means mounting the module on the steering wheel mounting bracket. The steering wheel mounting bracket has, in each mounting aperture, a spring finger which projects across the aperture. The base plate has a plurality of arcuately-spaced mounting apertures and three arcuately-spaced mounting studs projecting therefrom for insertion in the steering wheel mounting bracket apertures. The studs include retention surfaces which are captured by spring fingers upon insertion of the studs in the apertures to mount the base plate on the steering wheel mounting bracket. The air-bag has a mounting collar with three spaced holes therein for receiving the studs to mount the air-bag on the base plate. The cover has a plurality of arcuately-spaced flexible mounting tangs receivable in the base plate mounting apertures, each tang having a locking shoulder engageable with the base plate when assembled thereto. The inflator mounting flange has three slots for receiving the studs and includes a plurality of arcuately-spaced locking tabs, each one engageable with a locking tang when the inflator is assembled to the base plate to lock the cover and the base plate together by blocking removal of the tangs through the base plate mounting apertures. The inflator mounting flange has three spaced locking blades offset therefrom, and three mating openings in the base plate are sized to receive the locking blades therethrough. The base plate and the air-bag collar are trapped between the inflator locking blades and mounting flanges when the locking blades are projected through the openings and rotated out of alignment therewith. Also disclosed and claimed is a method of mounting an inflator, which has a peripheral mounting flange that includes at least two locking blades offset from the mounting flange, to an air-bag module base plate, which has mating openings sized to receive the inflator locking blades therethrough, which method comprises the steps of a) aligning each locking blade with a respective opening, b) engaging the inflator mounting flange with the base plate to project the locking blades through the respective openings, c) rotating the inflator relative to the base plate to move the locking blades away from the openings, thus trapping the base plate between the locking blades and the mounting flange to mount the inflator to the base plate and, preferably, d) rotating the inflator relative to the base plate in a direction to pass the locking blades over locking abutments adjacent each opening to trap the locking flange against reverse rotation. Additionally disclosed and claimed is a method of assembling an air-bag module which includes a cover, an apertured base plate, an air-bag having a collar, and an inflator, which method comprises the steps of a) pushing the cover onto the base plate to engage first locking surfaces on both, b) pushing a folded air-bag through the base plate aperture beneath the cover, and c) pushing the inflator through the aperture and twisting the inflator to engage second locking surfaces on the inflator and the base plate to clamp the inflator and base plate together with the air-bag collar clamped therebetween. These and further objects and features of this invention will become more readily apparent upon reference to the following detailed description of a preferred embodiment of the invention, as illustrated in the accompanying drawings, in which: Figure 1 is a partial perspective view of an automobile instrument panel showing a steering wheel which mounts an air-bag module according to the present invention; Figure 2 is a sectional plan view of the module, taken along line 2-2 of Figure 4, illustrating the assembly of an inflator to a base plate, with an air-bag deleted for clarity; Figure 3 is an exploded perspective view of the air-bag module shown in Figure 1; Figure 4 is an enlarged sectional view of the air-bag module shown in Figure 1, taken along line 4-4 of Figure 1; Figure 5 is an enlarged exploded perspective view of a portion of Figure 4, illustrating the mounting of the air-bag module to a steering wheel mounting bracket; Figures 6a and 6b are enlarged detail views of a circled area designated by "6" in Figure 2; Figure 7 is an enlarged cross-sectional view of a portion of Figure 2, taken along line 7-7 of Figure 2; and Figure 8 is a cross-sectional view of a portion of Figure 2, taken along line 8-8 of Figure 6b. As shown in Figure 1, an automobile passenger compartment contains therein an instrument panel 10 and a steering wheel assembly 11 including a steering wheel 12. Steering wheel assembly 11 includes a driver-side air-bag module 14 mounted centrally of the steering wheel 12. As best seen in Figures 3 and 4, air-bag module 14 comprises a cover 20, a base plate 40, an air-bag 70, and an inflator 80. Module cover 20 is decorative and is made of a vinyl plastics material or other synthetic plastics material which preferably matches steering wheel 12. It comprises a domed main body 22 which conventionally ruptures along a weakened door pattern (not shown) to enable air-bag deployment in a well-known manner when a predetermined vehicle deceleration occurs. A peripheral flange 24 depends from the main body 22 and terminates in a bottom edge 26 from which depend six circumferentially-spaced flexible locking tangs 28a, 28b, 28c, 28d, 28e and 28f. The locking tangs comprise respective tapered noses 30a, 30b, 30c, 30d, 30e and 30f that include respective locking shoulders 32a, 32b, 32c, 32d, 32e and 32f. Base plate 40 comprises a flat, circular body 42 having a central aperture 44 defined by an upturned flange 46 having three spaced cutout openings 48a, 48b and 48c, bounded by lanced locking abutments 50. Six spaced mounting apertures 52a, 52b, 52c, 52d, 52e and 52f are formed by lancing flanges 54a, 54b, 54c, 54d, 54e and 54f out of body 42. Base plate body 42 has three holes 56a, 56b and 56c punched in it for receiving three mounting studs 60a, 60b and 60c, best seen in Figures 4 and 5. Since all three studs are identical, only stud 60a will be described in detail. It has a cylindrical body 62a with a head 64a at one end and a tapered nose 66a at the other. Just behind nose 66a is a slot-like or notch 68a having a retention surface 69a. Holes 56a, 56b and 56c are sized to tightly receive therein respective studs 60a, 60b and 60c. Air-bag 70 is a conventional nylon bag which is illustrated in Figures 3, 4 and 5 as comprising a folded body 72 which has a central inflation opening 74. A mounting collar 76 is sewn to bag body 72 about opening 74 by stitching 78. Collar 76 includes spaced mounting holes 79 (only one illustrated) which receive studs 60a, 60b and 60c to mount air-bag 70 to base plate 40. Inflator 80 comprises a domed canister 82 having gas-discharge holes 84 about its periphery. Canister 82 is secured to a mounting flange 86 which has six spaced mounting tabs 88a, 88b, 88c, 88d, 88e and 88f which extend outwardly and are bent downwardly. Flange 86 also includes three sausage-shaped slots 90a, 90b and 90c for receiving studs 60a, 60b and 60c and three upwardly-lanced locking blades 92a, 92b and 92c. Air-bag module 14 is constructed for assembly without the use of the usual bolts, nuts and rivets. It is also designed for assembly which assures a predetermined orientation of cover 20, base plate 40, air-bag 70 and inflator 80 relative to each other in the module and for assuring a predetermined orientation of module 14 relative to steering wheel 12 on steering wheel assembly 11. This assures proper orientation of any graphics on cover 20 and any predetermined deployment of air-bag 70. To provide this predetermined orientation, cover tangs 28b and 28c are located closer to each other than to the other tangs. The corresponding base plate mounting apertures 52b and 52c are likewise located closer to each other, as are inflator mounting tabs 88b and 88c, all of which are mated when assembled. This assures the proper orientation of cover 20 upon assembly, which will now be explained, with particular reference to Figures 2 and 3. Studs 60a, 60b and 60c are inserted in holes 56a, 56b and 56c and are staked to base plate 40. Cover 20 is assembled by inserting locking tangs 28a, 28b, 28c, 28d, 28e and 28f through corresponding base plate mounting apertures 52a, 52b, 52c, 52d, 52e and 52f until flange edge 26 engages base plate body 42 and the locking tang shoulders 32a, 32b, 32c, 32d, 32e and 32f snap over the respective base plate flanges 54a, 54b, 54c, 54d, 54e and 54f. Base plate stud-mounting holes 56a, 56b and 56c are unequally spaced about base plate body 42. Air-bag collar holes 79 are spaced accordingly, as are inflator slots 90a, 90b and 90c, to accommodate studs 60a, 60b and 60c during assembly. Folded air-bag 70 is aligned and pushed through base plate aperture 44 with holes 79 receiving studs 60a, 60b and 60c until collar 76 engages base plate body 42. Inflator 80 is assembled by aligning locking blades 92a, 92b and 92c with respective base plate openings 48a, 48b, and 48c, as shown in Figures 2 and 6a. This also aligns studs 60a, 60b and 60c with respective inflator slots 90a, 90b and 90c. Canister 82 is pushed through aperture 44 until flange 86 engages air-bag collar 76 against base plate body 42. This moves blades 92a, 92b and 92c through openings 48a, 48b and 48c on the other side of body 42, as shown in Figure 7. Inflator 80 is then twisted, i.e. rotated, clockwise (as seen in Figures 2 and 6b) to force blades 92a, 92b and 92c over and beyond abutments 50 to spring back into engagement with base plate body 42, as shown in Figure 8. This locks blades 92a, 92b and 92c against reverse rotation and locks inflator 80 to base plate 40 by trapping body 42 between blades 92a, 92b, 92c and flange 86. It also tightly clamps air-bag collar 76 between base plate body 42 and inflator flange 86. The rotation of inflator 80 also positions locking tabs 88a, 88b, 88c, 88d, 88e and 88f in contact with the backs of respective cover tangs 28a, 28b, 28c, 28d, 28e and 28f, thus locking them into contact with base plate flanges 54a, 54b, 54c, 54d, 54e and 54f and preventing their disassembly back through mounting apertures 52a, 52b, 52c, 52d, 52e and 52f. Elongated slots 90a, 90b and 90c accommodate inflator movement relative to studs 60a, 60b and 60c during this simple "push and twist" assembly. Air-bag module 14 is now fully assembled and ready for installation to steering wheel 12. Referring to Figures 3, 4 and 5, steering wheel assembly 11 includes a steering column 100. Steering column 100 clamps a mounting bracket 102 between a plate 104 and a nut 106 which engages a threaded end 108 of steering column 100. Bracket 102 is apertured at three spaced locations. Each aperture has mounted therein an identical retaining unit 110 having a central hole 112. A spring finger 114 mounted in a notch 116 projects into hole 112. To orient air-bag module 14 relative steering wheel 12, retaining units 110 have the same unequal spacing as studs 60a, 60b and 60c on module 14. This assures only one possible assembly orientation of module 14 on the steering wheel assembly 11. Studs 60a, 60b and 60c are aligned with, and pushed through, respective holes 112. Upon insertion, stud noses 66a, 66b and 66c displace the respective spring fingers 114 aside to enable full stud insertion. When stud notches 68a, 69b and 68c register with the respective spring fingers 114, spring fingers 114 snap into them and engage notch retention surfaces 69a, 69b and 69c to lock the studs against removal. This locks the air-bag module 14 to steering column 100. Thus, this invention provides a driver-side air-bag module that is easily and quickly assembled and uses no fasteners. Instead, locking surfaces on the module components lock them together with a sequence of only a "push" action (to secure the cover to the base plate), a "push" action (to secure the air-bag to the base plate within the cover), and a "push-and-twist" action (to secure the inflator to the base plate). The module is then easily installed to the steering wheel assembly with a final "push" action.

Claims: An air-bag module (14) mountable to a steering wheel assembly (11) having a mounting bracket (102), said air-bag module (14) comprising a base plate (40), an air-bag (70), a cover (20) and an inflator (80), characterised in that the base plate (40) has a plurality of arcuately-spaced mounting apertures (52a,52b,52c,52d,52e,52f); the air-bag (70) has a mounting collar (76); the cover (20) has a plurality of arcuately-spaced flexible locking tangs (28a,28b,28c,28d,28e,28f) receivable in the respective base plate mounting apertures (52a,52b,52c,52d,52e, 52f), each tang having a locking shoulder (32a,32b,32c,32d,32e,32f) engageable with the base plate (40) when assembled thereto; the inflator (80) has a mounting flange (86) including a plurality of arcuately-spaced mounting tabs (88a,88b,88c,88d,88e, 88f) each one engageable with a respective locking tang (28a,28b,28c,28d,28e,28f) of the cover (20) when the inflator (80) is assembled to the base plate (40) so as to lock the cover (20) and the base plate (40) together by blocking removal of the tangs (28a,28b,28c,28d,28e, 28f) of the cover (20) through the base plate mounting apertures (52a, 52b,52c,52d,52e,52f); there are co-operating locking means (48a,48b,48c,92a,92b,92c) on the inflator mounting flange (86) and the base plate (40) for securing the inflator (80) to the base plate (40); there are air-bag securing means (60a,60b,60c) securing the air-bag mounting collar (76) to the assembled air bag module (14); and there are fastening means (60a,60b,60c) carried by the air bag module (14) for attaching the module (14) to the steering wheel mounting bracket (102). An air-bag module (14) according to claim 1, in which the co-operating locking means comprise a locking blade (92a,92b,92c) offset from the inflator mounting flange (86) and an opening (48a,48b,48c) in the base plate (40) sized to receive the inflator locking blade (92a,92b,92c) therethrough, the base plate (40) being trapped between the locking blade (92a,92b,92c) and the inflator mounting flange (86) when the locking blade (92a,92b,92c) is projected through the opening (48a,48b,48c) and rotated out of alignment therewith. An air-bag module (14) according to claim 1, in which the co-operating locking means comprise three spaced locking blades (92a,92b,92c) offset from the inflator mounting flange (86) and three mating openings (48a,48b,48c) in the base plate (40) sized to receive the locking blades (92a,92b,92c) therethrough, the base plate (40) being trapped between the inflator locking blades (92a,92b,92c) and the inflator mounting flange (86) when the locking blades (92a,92b,92c) are projected through the respective openings (48a,48b,48c) and rotated out of alignment therewith. An air-bag module (14) according to claim 3, in which the base plate (40) includes a locking abutment (50) adjacent each opening (48a,48b, 48c), and the locking blades (92a,92b,92c) are forced over the abutments (50) and spring back into contact with the base plate (40) after rotation to trap the locking blades (92a,92b,92c) against reverse rotation. An air-bag module (14) according to claim 1, in which the fastening means comprise a plurality of spaced mounting studs (60a,60b,60c) projecting from the assembled module (14) for insertion in mating apertures (112) in the steering wheel mounting bracket (102) and which include retention surfaces (69a,69b,69c) captured by co-operating retaining means (114) on the steering wheel mounting bracket (102). An air-bag module (14) according to claim 5, in which the air-bag securing means comprise mounting holes (79) in the air-bag collar (76) for receiving the mounting studs (60a,60b,60c) to trap the air-bag collar (76) between the base plate (40) and the inflator mounting flange (86). An air-bag module (14) according to claim 5, in which the mounting studs (60a,60b,60c) and mating steering wheel mounting bracket apertures (112) are unequally spaced to assure a predetermined orientation of the module (14) to the steering wheel (12) when assembled thereto. An air-bag module (14) according to claim 5, in which each stud (60a) has a cylindrical body (62a) terminating in a tapered nose (66a), the retention surfaces comprise a notch (68a) in the side of the stud (60a) behind the nose (66a), and the retaining means comprise spring fingers (114) projecting across the mating apertures (112) that are displaced aside by the tapered noses (66a,66b,66c) to enable insertion of the studs (60a,60b,60c) into the mating apertures (112), and which snap into the notches (68a,68b,68c) when the studs (60a,60b,60c) are fully inserted. An air-bag module (14) according to claim 1, in which one base plate mounting aperture (52b) and one corresponding cover locking tang (28b) are unequally spaced from their adjacent apertures (52a,52c) and tangs (28a,28c) to assure a predetermined orientation of the cover (20) relative to the base plate (40) when assembled thereto. An air-bag module (14) according to claim 1, in which the steering wheel assembly mounting bracket (102) has spaced mounting apertures (112); there are three spring fingers (114) mounted on the steering wheel mounting bracket (102), each one of which projects into a respective aperture (112); the base plate (40) has three arcuately-spaced mounting studs (60a,60b,60c) projecting therefrom for insertion in the respective steering wheel mounting bracket apertures (112) which studs (60a,60b,60c) include retention surfaces (69a,69b,69c) captured by the spring fingers (114) upon insertion of the studs (60a,60b,60c) in the respective apertures (112) to mount the base plate (40) on the steering wheel mounting bracket (102); the air-bag (70) has a mounting collar (76) with three spaced holes (79) therein for receiving the studs (60a,60b,60c) to mount the air-bag (70) on the base plate (40); the inflator mounting flange (86) has three slots (90a,90b,90c) for receiving the studs (60a,60b,60c); the inflator mounting flange (86) has three spaced locking blades (92a,92b,92c) offset therefrom, and there are three mating openings (48a,48b,48c) in the base plate (40) sized to receive the locking blades (92a,92b,92c) therethrough, the base plate (40) being trapped between the inflator locking blades (92a,92b,92c) and the inflator mounting flange (86) and the air-bag mounting collar (76) being clamped between the inflator mounting flange (86) and the base plate (40) when the locking blades (92a,92b,92c) are projected through the respective openings (48a,48b,48c) and rotated out of alignment therewith. A method of mounting an inflator (80), which has a peripheral mounting flange (86) that includes at least two locking blades (92a,92b) offset from the mounting flange (86), to an air-bag module base plate (40), which has mating openings (48a,48b) sized to receive the inflator locking blades (92a,92b) therethrough, characterised in that the method comprises the steps of a) aligning the locking blades (92a,92b) with the respective openings (48a,48b), b) engaging the inflator mounting flange (86) with the base plate (40) to project the locking blades (92a,92b) through the respective openings (48a,48b), and c) rotating the inflator (80) relative to the base plate (40) to move the locking blades (92a,92b) away from the respective openings (48a,48b) and over the base plate (40), thus trapping the base plate (40) between the locking blades (92a,92b) and the inflator mounting flange (86) so as to mount the inflator (80) to the base plate (40). A method according to claim 11, in which the base plate (40) includes a locking abutment (50) adjacent each opening (48a,48b), and the method includes the further step of d) rotating the inflator (80) relative to the base plate (40) in a direction to pass the locking blades (92a,92b) over the locking abutments (50) to trap the locking blades (92a,92b) against reverse rotation. A method of assembling an air-bag module (14) which comprises a cover (20), an apertured base plate (40), an air-bag (70) having a collar (76) and an inflator (80), characterised in that the method comprises the steps of a) pushing the cover (20) onto the base plate (40) to engage first locking surfaces (32,54) on both, b) pushing the folded air-bag (70) through a base plate aperture (44) beneath the cover (20), c) pushing the inflator (80) through the aperture (44) and twisting the inflator (80) to engage second locking surfaces (48,92) on the inflator (80) and the base plate (40) to clamp the inflator (80) and base plate (40) together with the air-bag collar (76) clamped therebetween. A method according to claim 13, in which twisting the inflator (80) also blocks disengagement of the first locking surfaces (32,54).

Inventors: BOWSER ROBERT EDWARD, GORDON JOHN ERIC, HUFFMAN ROBERT EUGENE, SCHENCK DAVID PATRICK, SPARKMAN JOHN PAUL, STUKENBORG STEVEN WILLIAM, BOWSER, ROBERT EDWARD, GORDON, JOHN ERIC, HUFFMAN, ROBERT EUGENE, SCHENCK, DAVID PATRICK, SPARKMAN, JOHN PAUL, STUKENBORG, STEVEN WILLIAM
Applicants: GEN MOTORS CORP, GENERAL MOTORS CORPORATION
Application year: 1994
Main classification: B60R21
IPC codes: B60R21